The present invention relates to a method and converter arrangement for compensating nonlinearities introduced by transmission members in a radio relay transmission system.
A previously proposed system of this type which provides nonlinearity compensation is described in Federal Republic of Germany Application De. No. 27 43 352. This system includes a harmonic generator converter stage to which is fed an intermediate frequency signal (ZF) modulated with the useful signal and a local oscillator signal. The stage includes a first converter diode setting the high frequency (HF) signal with its desired level, a second converter diode setting the HF signal below its desired level and with a shift in phase, and means linking the two HF signals with the setting being selected in such a manner that the linked high frequency output signal has a distorted component whose amplitude coincides with the amplitude of the distorted signal component created by a transmission member but whose phase is in phase opposition to the latter.
The purpose of the previously proposed system is to compensate for the nonlinearity introduced by the transmission member by suitably dimensioning a converter. To this end, a variable series circuit tuned to the oscillator frequency and including an inductance, a capacitance and a resistor is provided for changing the level and phase of the oscillator signal.
A drawback of this approach, however, is that the series circuit will have to be retuned upon each change in frequency and the phase position of the generated nonlinearity is limited to a range from--.pi./4&lt;.omega.&lt;.pi./4.